1. Field of the Invention
This invention relates to an ionization apparatus and to an ionization analysis apparatus utilizing barrier discharge.
2. Description of the Related Art
Examples of an ionization analysis method and apparatus utilizing barrier discharge are described in the following literature:
Na Na, Chao Zhang, Mengxia Zhao, Sichun Zhang, Chengdui Yang, Xiang Fang and Xinrong Zhang, “Direct detection of explosives on solid surfaces by mass spectrometry with an ambient ion source based on dielectric barrier discharge”, J. Mass Spectrom. 2007; 42:1079-1085
Na Na, Mengxia Zhao, Sichun Zhang, Chengdui Yang and Xinrong Zhang, “Development of a Dielectric Barrier Discharge Ion Source for Ambient Mass Spectrometry”, J Am Soc Mass Spectrom. 2007, 18, 1859-1862
The ion analysis method and apparatus described in these references have a plate-shaped electrode, a glass plate placed on the surface of the plate-shaped electrode and a needle-shaped electrode disposed substantially perpendicular to the surface of the glass plate (the plate-shaped electrode) and spaced away from the glass plate, and impress an alternating high-voltage across the plate-shaped electrode and needle-shaped electrode and induce a barrier discharge. A sample serving as an object to undergo analysis is placed on the glass plate and is exposed to a plasma torch produced by the barrier discharge. As a result, atoms and molecules are desorbed from the sample and ionized. The ions generated are introduced to a mass analysis apparatus and analyzed.
With the ionization methods described in the above-mentioned literature, ionization of the sample is carried out in a space that is open to the atmosphere. Many of the ions generated, therefore, diffuse into the atmosphere and only some of them are introduced into the mass analyzer. Sensitivity is sacrificed as a result.